An angelfish at the Denver Zoo was "swimming abnormally." A special CT scan revealed the reason why.

A fancy-looking French angelfish that was found one day with a funny float has its buoyancy back after taking some time from its tropical trappings to get a CT scan at the Denver Zoo.

A zoo worker recently noticed the blue and yellow fish was "experiencing buoyancy issues and swimming abnormally" with a tilt, the zoo said. That prompted a visit last week to the facility's on-site hospital for an ultrasound and the CT scan.

The CT scan took place in a machine large enough to fit a 700-pound grizzly bear, so some special accommodations were required, zoo spokesperson Jake Kubie said. The approximately seven-inch fish was sedated, balanced upright on a sponge and had water poured over its gills to keep it alive as the scan took place.

The diagnosis: Too much gas. Enteritis, or inflamed intestines, had resulted in increased internal gas that was affecting the fish's buoyancy, Kubie said.

"It was treated with antibiotics," he said. "It's doing much better and swimming normally."

The zoo posted photos of the unusual CT scan on Instagram.

"From the tiniest tree frog to a full-grown grizzly bear, we're proud to offer the highest level of care to our animal residents!" the zoo wrote on Instagram.

According to Oceana, French angelfish are foragers that eat a variety of invertebrates and plants. Juvenile angelfish clean parasites and loose scales off of large fish.

The unusual CT scan at the Denver Zoo comes just weeks after a 376-pound alligator that was "behaving strangely" at a Florida zoo was diagnosed with an ear infection after CT scans and X-rays.

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• Denver Zoo